1. Field of the Invention:
The present invention relates to a method of preventing or eliminating the foaming of polymeric dye-containing aqueous solutions, particularly soft drink compositions, by use of glycerol monooleate, glycerol dioleate or a mixture thereof.
2. Description of the Prior Art:
Polymeric dyes have been recently proposed as satisfactory replacements for FD&C REd #2, which can no longer be used in foods, drugs and cosmetics in the United States. When polymeric colors are used in edibles, if the size of the molecules of polymeric color exceeds a certain limit--usually a molecular size of from about 1000 to 2000 Daltons--and if the color compounds do not break down and thus maintain this size, the polymeric colors are not absorbed through the walls of the gastrointestinal tract. This means that when such materials are consumed, they essentially pass directly through the gastrointestinal tract. They are not taken into the body or its systemic circulation and thus any risk of possible systemic toxicity is eliminated. An excellent red polymeric colorant, which shows promise as an especially desirable replacement for existing red food colors such as FD&C Red #2, is an anthrapyridone known as Poly R.TM. -481. Poly R.TM. -481 is an acetylated version of a colorant having the structural formula ##STR1## wherein about 95% of the free backbone amines have been converted to ##STR2## groups and wherein A+B+D equals about 900 (A equals about 180, B equals about 360 and D equals about 360). Equivalent to Poly R.TM. -481 for the purposes of this invention are the corresponding polymeric colorants wherein about 80 to 98% of the free backbone amines have been acetylated.
Poly R.TM. -481 can be prepared by a reaction sequence which begins with 1-amino-2-methyl-4-bromoanthraquinone. That material is reacted with phenylacetyl chloride, suitably in an aprotic organic solvent such as toluene, at an elevated temperature. The resultant addition product of the formula ##STR3## is then cyclized with base to afford a compound of the formula ##STR4## which is then reacted with vinylamine-vinylsulfonate copolymer. This amine displacement is an adaption of the classic Ullmann reaction and is carried out in water or mixed water/organic solvent and base and with a copper catalyst such as Cu.sub.2 Cl.sub.2. The resultant polymer of formula (I) is then acetylated by reacting it with acetic anhydride in aqueous base. The red solution thus obtained yields, after lyophilization, a solid red product corresponding to formula (I) except that about 95% of the free backbone amines have been converted to ##STR5## groups. Poly R.TM. -481 and related anthraquinones are disclosed and claimed in U.S. patent application Ser. No. 751,857, filed Dec. 17, 1976, assigned to the assignee hereof, and hereby expressly incorporated by reference in its entirety and relied upon.
The use of Poly R.TM. -481 in aqueous solutions, particularly in carbonated beverages, has unfortunately been limited by the excessive foaming which has been observed in such solutions. Foaming is considered a significant drawback to the use of this polymeric dye in carbonated beverages since it would result in filling problems during high-speed bottling operations. Foaming could result in excessive spillage and short-filled packaging in both bottling and canning operations.